1. Field of the Invention
The present invention relates in general to an engine, and in particular to a component layout for a marine engine, including an arrangement of the fuel injectors within the engine.
2. Description of Related Art
Internal combustion engines are commonly used to power small watercraft such as personal watercraft. These watercraft include a hull which defines an engine compartment. The engine is positioned in the engine compartment. The output shaft of the engine is coupled to a water propulsion device of the watercraft, such as an impeller.
Air must be supplied to the engine from outside the hull for use in the combustion process. Typically, air flows through one or more ducts in the hull into the engine compartment, and then through an intake system of the engine to the combustion chamber(s) of the engine.
Fuel is also supplied to the engine for use in the combustion process. In order to accurately meter the fuel and improve engine operating efficiency and performance, the fuel is injected with one or more fuel injectors. In this arrangement, fuel is supplied to the fuel injectors at high pressure. Each injector has an electrically operated valve which selectively opens and closes, controlling the flow of fuel through the injectors to the engine.
Personal watercraft also commonly include an access opening that is formed in the watercraft deck above the engine. A longitudinally extending, straddle-type seat normally covers the access opening to close the engine compartment and prevent an influx of water. On occasions, however, a rider may need to open the access opening while the watercraft is floating in a body of water in order to make minor repairs or adjustments.
Prior arrangements of the fuel injectors within the engine compartment pose the risk that water may enter the engine compartment through the open access opening and contact the fuel injectors, which can damage the fuel injectors and/or their electrical contacts. In addition, water that enters the engine compartment may also splash about within the watercraft hull due to the pitching and rocking movement of the watercraft as it moves through the water. In either event of direct contact or of subsequent internal splashing, the water can corrode the injector and/or interrupt the electrical current flow to the injectors. This may permanently damage the injectors as well as may affect the operation of the engine.
In order to keep the size of the watercraft small and the center of gravity low, the engine compartment is made very small, thus necessitating that the engine be compact. One problem with this arrangement is that hot exhaust gases flowing through the exhaust system from the engine may be routed very close to other components of the engine, damaging them or resulting in their poor performance. This is true of the fuel injectors, where the heat from the exhaust system may damage the injector and shorten its useful life.
Some prior watercraft have increased the width of the watercraft in order to separate the fuel injectors from the exhaust system. The associated engines have also employed a wider width in order to provide a component arrangement wherein the position of the intake pipe(s) does not interfere with the position of the fuel injectors and the associated fuel supply rail. Such watercraft, however, sacrifice the handling performance due to the resulting wider hull; the wider watercraft cannot turn as sharp.
These problems related to component arrangement are further exacerbated when multiple fuel injectors are used with each cylinder of the engine. Some personal watercraft engines recently have employed multiple fuel injector with each cylinder in an effort to enhance engine output power. It has been thought, however, that the use of multiple fuel injectors would result in a wider engine. Hence, watercraft designers have had to balance top end performance against handling performance.